Various machines include hydraulic systems with motors and other hydraulic components, including cylinders, configured to be activated by an operator using various forms of operator controls. One form of control is known as a joystick, which often controls at least two separate functions with a single control lever. For instance, one function is typically controlled by fore-aft movement of the control lever, while another function is controlled by lateral movement. One example of separate functions controlled by a single joystick involves a loader mechanism having a lift cylinder and a bucket cylinder. The lift cylinder raises and lowers a bucket and the bucket cylinder rotates the bucket around a pivot axis for dumping. The bucket is operated by controlling the direction of flow and the rate of flow of hydraulic fluids to the lift and bucket cylinders. A common control system arrangement utilizes fore-aft movement of the joystick to control the lift cylinder, and lateral movement to control the bucket cylinder. If the joystick is pushed forward, away from the operator, the lift cylinder lowers the bucket; when pulled toward the operator, the lift cylinder raises the bucket. If the joystick is pushed to the right, the bucket cylinder rotates the bucket to dump material; when pulled to the left, the bucket cylinder rotates the bucket to load material or retain material within the bucket.
Typically, the flow rate and resulting speed of the associated functions are related to the travel of the joystick. As the joystick moves further from a centered position, the flow rate increases and the speed of the function increases. Operation of machines having this type of operator control requires the operator to move the joystick in a proper direction, and to move the joystick a proper distance.
Often, when operating a mobile machine, the operator is subjected to the movement of the machine. On rough terrain or surfaces, it can be difficult to control the position of the joystick. This problem is pronounced with some machines, such as compact skid steer loaders or compact tool carriers. In operating these machines, the operator either walks along with the machine, or stands on the back of the machine, while operating the controls. An example of a prior art control system for the type of machine where the operator walks along with the machine is disclosed in U.S. Pat. No. 6,460,640 to Keagle et al. In either case, it can be difficult to precisely control the machine while riding or walking over rough terrain, and while performing multiple machine operations. In general, an improved control arrangement is needed.